Criticism of Jay Joseph on Twin Studies and psychiatry

The Trouble win Twin Studies: A Reassessment of Twin Research in the Social and Behavioral Sciences by Jay Joseph is about twin research and the way psychiatrists try to use it to argue that some behaviour is controlled by genes. It illustrates some bad misconceptions about evolution. It also includes misconceptions about the sort of arguments that are worth making against psychiatry.

Knowledge about what you want to do and how you want to do it is what explains the stuff you do. Anything else is just a particular circumstance in which you use the knowledge you already have. If you go to the supermarket and they have run out of hummus and buy some other snack instead that doesn’t necessarily change your preferences, it just changes what you do in that particular situation. So then what matters for assessing behavioural genetics is concerned is what knowledge you use to make decisions and the properties of that knowledge.

Evolution is a knowledge-creating process. Genes contain information about how to set up an organism that will make copies of those genes. That knowledge was created by variation and selection of genes. The variation takes place by genes mutating. The selection consists of genes either managing to make bodies that make copies of those genes, or not. The fact that copies are made of the successful variants of genes is important because otherwise there is no way for many small changes to build up over evolutionary time. If every small change was lost to the next generation, then no knowledge would be created because there wouldn’t be any selection.

For humans, genetics is irrelevant to behaviour, assertions to the contrary notwithstanding. People think and make decisions and have ideas: culture. Culture is also a knowledge creating process. A person produces some variation on current knowledge. That variation either manages to get copied in books, in people talking about it and thinking about it, or it doesn’t get selected and it dies. This has led some people, like Richard Dawkins to suggest that evolving ideas should be treated as analogous to genes in some ways:  he called the evolving ideas memes. The best existing treatment of memes is in The Beginning of Infinity by David Deutsch. A person can change his mind a lot faster than he can change his genes. And the selection process for an idea doesn’t necessarily involve implementing the idea immediately. So an idea can go through a phase in its development where it couldn’t be implemented without the idea being destroyed. As such, if a gene and an idea address the same issue the idea will evolve faster and the selection pressure on the gene will cease. These differences mean that ideas explain differences in behaviour between people, not genes.

Jay Joseph makes a different argument against behavioural genetics. On pp. 99-100 of the Joseph book he writes:

In recent years much attention has focused on epigenetics, which refers to genes switching expression on and off in response to environmental events and challenges, without alteration in the DNA sequence. Furthermore, these epigenetic changes can be passed down to the next generation independently of DNA inheritance. As the psychologist John Read and his colleagues Richard Bentall and Roar Fosse put it, “epigenetic processes turn gene transcription on and off through mechanisms that are highly influenced by the individual’s socio-environmental experiences.” They believed that “the implications, for research, mental health services and primary prevention, are profound” (Read, Bentall, & Fosse, 2009, p. 299).

…

Although some genetically oriented researchers have attempted to integrate epigenetics into their existing arguments and theories (e.g., Plomin, DeFries, et al., 2013, pp. 146–149), recent findings in epigenetics and other areas provide additional support to environmental theories of behavioral differences. This is because it is now known that the environment, and especially the perinatal environment, can influence gene expression. This is, according to Charney, “particularly prevalent in the human brain and probably [is] involved in much human behavior” (Charney, 2012, p. 331; see also Meaney, 2010).

If epigenetic changes can be inherited then that’s just more of the same kind of things that genes do. Epigenetics is sometimes described just in terms of the influence of some genes switching on and off in a way that changes the activity of other genes. In that scenario, epigenetic is not any kind of exception to genetics, it is just a consequence of the content your genes. However, suppose are some inherited non-genetic chemicals as some people claim: call them epigenes. You just use the epigenes in addition to genes to explain behaviour. They act in almost exactly the same way as genes. They only go through selection once per generation. They can only act by building something that works first time. Any differences are minor compared to these similarities. The twin study people could respond by saying they’ll just test for these epigenes too.

If the epigenes can’t be inherited they don’t contain much knowledge since there is no opportunity for error correction, so they can’t be very important for behaviour, as in the “supermarket is out of hummus” example.

What about psychiatry? Trying to argue that there’s a different biological mechanism for behaviour than those psychiatrists talk about doesn’t matter at all for reform of psychiatry. Let’s say that Joseph totally won the argument and psychiatrists started looking for epigenetic stuff and trying to “treat” it. That, in and of itself, wouldn’t matter at all. Who cares whether psychiatrists use your genes or what happened to you in the womb as an excuse for involuntary treatment? The psychiatrists would still be treating people involuntarily unless you argue specifically against involuntary treatment. This is a moral issue not a scientific issue and you can’t settle it by arguing solely about whether X causes Y. You have to argue that a person is morally responsible for his behaviour, and that imprisoning a person without trial is wrong, and those are moral and philosophical issues, not scientific issues.